Generally speaking, the external ventricular drainage system includes a container and a pressure valve connecting the container to a brain chamber. When the brain pressure inside the brain chamber is too large, the pressure valve will be opened, such that the liquid inside the brain chamber can be drained to the container. Different medical orders are provided in response to the change in the liquid level (the brain fluid volume) of the brain fluid inside the container. The medical staff need to be on site to physically observe the change in the liquid level of the brain fluid inside the container and determine what corresponding medical order needs to be taken.
Therefore, how to provide a device or a method capable of automatically detecting relevant change in liquid level has become a prominent task for the industries.